JP2006196514A - Semiconductor device and its fabrication process - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To form a gettering region without performing an ion implantation process. <P>SOLUTION: The semiconductor device comprises an SOI substrate 1 where a semiconductor active layer 1c is formed on a semiconductor wafer 1a through a pasted insulating film 1b, an insulating film 5 arranged in an isolation region 8 around the element forming region 9 of the SOI substrate 1 and on the semiconductor active layer 1c while having a plurality of meshed openings 5a, and a gettering region 6 arranged in a semiconductor active layer 1a in the vicinity of the opening 5a. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a semiconductor device using an SOI substrate and a manufacturing method thereof, and more particularly to a semiconductor device having a gettering region that captures contaminants such as heavy metals and a manufacturing method thereof.

  A semiconductor device using an SOI (Silicon On Insulator) substrate in which a semiconductor active layer is formed on a semiconductor wafer by bonding an insulating film operates at a high speed even with a low voltage power source. Therefore, application to a low power consumption LSI has been studied. ing. In a semiconductor device using such an SOI substrate, the thickness of the semiconductor active layer is as thin as about 10 μm, and this semiconductor active layer is entirely a defect-free region, and a bonded insulating film is formed under the semiconductor active layer. There is. In such a configuration, contaminants such as heavy metals in the manufacturing process are not captured (absorbed; gettered) by the semiconductor active layer, and the bonded insulating film prevents the contaminants from passing through. The back surface of the substrate (the back surface of the semiconductor wafer in the SOI substrate) cannot be used as a gettering site (crystal defect, strained layer, stress field). Therefore, contaminants are left in the semiconductor active layer on the bonded oxide film, and leakage current is generated in the element formed on the SOI substrate, and the film quality of the gate oxide film is deteriorated. May adversely affect the devices formed. Specifically, the element formed on the SOI substrate has a smaller Qbd (Charge to breakdown) of the gate oxide film than the element formed on the normal wafer. Therefore, in a semiconductor device using an SOI substrate, it is necessary to effectively capture contaminants and improve element reliability. In view of the necessity, a semiconductor device using an SOI substrate in which a gettering region is formed in an element isolation region is disclosed (see Patent Document 1).

  In the semiconductor device described in Patent Document 1, the gettering region is formed as follows. First, an SOI substrate 101 is prepared in which a semiconductor active layer 101c (p-type or n-type) is formed on a semiconductor wafer 101a through a bonding insulating film 101b. The semiconductor active layer 101c is divided into island shapes by a separation groove 112 reaching the bonded insulating film 101b, and the separation groove 112 is filled with polysilicon through an oxide film (see FIG. 4A). Next, an oxide film 102 is formed on the SOI substrate 101, a nitride film 103 is formed on the oxide film 102, a photoresist 104 is coated on the nitride film 103, and patterning and etching are performed on the element isolation region 113. The nitride film 103 and the photoresist 104 are removed (see FIG. 4B). Thereafter, using the photoresist 104 and the nitride film 103 as a mask, ion implantation is performed by ionizing oxygen atoms or Si atoms into the element isolation region 113 below the oxide film 102 (see FIG. 4C). Subsequently, after removing the photoresist 104, a LOCOS (Local Oxidation of Silicon) oxide film 109 is formed in the element isolation region 113 by thermal oxidation, and the nitride film 103 and the oxide film 102 are removed (FIG. 4D). reference). When the ion-implanted material is oxygen atoms, a region in which part of the oxygen atoms is precipitated in the element isolation region 113 by thermal oxidation or subsequent heat treatment becomes the gettering region 108 (gettering site). When the ion-implanted material is Si atoms, local stress is generated by Si atoms during the crystallization process by heat treatment to form crystal defects, and a region where the crystal defects are formed is a gettering region 108 (gettering site). ) In this manner, the gettering region 108 formed under the LOCOS oxide film 109 in the element isolation region 113 can capture (getter) contaminants such as heavy metals introduced when forming the semiconductor element. is there.

JP 11-297703 A

  However, in the method of manufacturing a semiconductor device described in Patent Document 1, an ion implantation step of oxygen atoms or Si atoms is necessary to form a gettering region, which may make the manufacturing process redundant.

  An object of the present invention is to make it possible to form a gettering region without performing an ion implantation process for the gettering region.

  In a first aspect of the present invention, in a semiconductor device, an SOI substrate in which a semiconductor active layer is formed on a semiconductor wafer through a bonding insulating film, and an element isolation region around the element formation region of the SOI substrate are arranged. And an insulating film disposed on the semiconductor active layer and having a plurality of mesh or line openings, and a gettering region disposed in the semiconductor active layer in the vicinity of the openings, It is characterized by providing.

  According to a second aspect of the present invention, in a semiconductor device, a LOCOS oxide having a plurality of openings formed in a semiconductor active layer and an element isolation region on the semiconductor active layer and partitioning an element formation region. And a gettering region formed in the semiconductor active layer under the LOCOS oxide film corresponding to the opening.

  In a third aspect of the present invention, in the method of manufacturing a semiconductor device, a step of forming a silicon oxide film and a silicon nitride film on an SOI substrate in which a semiconductor active layer is formed on a semiconductor wafer through a bonding insulating film; Forming a photoresist on the entire surface of the element formation region of the SOI substrate on the silicon nitride film and in the element isolation region in a mesh or a line; and using the photoresist as an etching mask, the semiconductor Etching at least the silicon oxide film and the silicon nitride film until the active layer appears, and after removing the photoresist, gettering is performed on the element isolation region by thermal oxidation using the silicon nitride film as a mask. Forming a LOCOS oxide film having a plurality of mesh-like or line-like openings for forming a region; Characterized in that it comprises a step.

  According to the present invention, it is possible to provide a highly reliable device capable of effectively capturing contaminants such as heavy metals without newly adding special processes in an SOI substrate.

(Embodiment 1)
A semiconductor device according to Embodiment 1 of the present invention will be described with reference to the drawings. 1A is a partial cross-sectional view schematically showing a configuration of a semiconductor device according to Embodiment 1 of the present invention, and FIG. 1B is a partial plan view thereof.

  This semiconductor device is a semiconductor device having a gettering region 6 on an SOI substrate 1, and includes an SOI substrate 1, a LOCOS oxide film 5, a gettering region 6, an isolation groove 7, an element isolation region 8, and an element formation. Region 9. Note that FIG. 1 shows an intermediate of a semiconductor device for convenience of explanation.

  The SOI substrate 1 is a substrate in which a semiconductor active layer 1c is formed on a semiconductor wafer 1a through a bonding insulating film 1b. The semiconductor active layer 1c is made of p-type or n-type silicon single crystal and will become a p-type or n-type well region in the future. The LOCOS oxide film 5 is a silicon oxide film (insulating film) formed on the semiconductor active layer 1 c by the LOCOS method, and is formed in the element isolation region 8. The LOCOS oxide film 5 is formed in a mesh shape (net shape) when viewed from the plane direction, and has a plurality of openings 5a formed in a mesh shape (island shape). The gettering region 6 is a region that captures contaminants such as heavy metals. The gettering region 6 is disposed in and near the opening 5a of the LOCOS oxide film 5 in the element isolation region 8 when viewed from the planar direction, and is opened when viewed from the cross-sectional direction. The semiconductor active layer 1c is also disposed in the semiconductor active layer 1c near the portion 5a and under the LOCOS oxide film 5 near the opening 5a. The isolation trench 7 is a trench for isolating adjacent element formation regions, is formed in the semiconductor active layer 1c, and has a depth up to the bonded insulating film 1b. A silicon oxide film 7a is formed on the inner wall surface of the isolation trench 7, and polysilicon 7b is embedded in the silicon oxide film 7a. The element isolation region 8 is a region for isolating adjacent element formation regions. The element isolation region 8 is arranged around the element formation region 9 in a region surrounded by the isolation groove 7 when viewed from the plane direction, and the LOCOS oxide film 5. The region to be the opening 5a is also included. The element formation region 9 is a region for forming an element, is surrounded by the element isolation region 8 when viewed from the plane direction, and does not include a region that becomes the opening 5a of the LOCOS oxide film 5.

  Next, a method for manufacturing a semiconductor device according to the first embodiment of the present invention will be described with reference to the drawings. 2 and 3 are process partial cross-sectional views schematically showing the method for manufacturing the semiconductor device according to the first embodiment of the present invention.

  First, an SOI substrate 1 in which a semiconductor active layer 1c is formed on a semiconductor wafer 1a with a bonding insulating film 1b interposed therebetween is prepared (see FIG. 2A).

  Next, a silicon oxide film 2 is formed on the semiconductor active layer 1c, a silicon nitride film 3 is formed on the silicon oxide film 2, a photoresist 4 is coated on the silicon nitride film 3, and a photoresist is formed by photolithography. 4 is patterned into a predetermined shape (see FIG. 2B). Here, the photoresist 4 is formed on an element formation region 9 and a region to be an opening of the LOCOS oxide film (5a in FIG. 2D) in the future as viewed from the planar direction.

  Next, the silicon nitride film 3 and the silicon oxide film 2 (and a part of the semiconductor active layer 1c) are removed by dry etching using the photoresist 4 as an etching mask until the semiconductor active layer 1c appears (FIG. 2 (FIG. 2 ( C)). In order to obtain a planar LOCOS structure in which the surface of the LOCOS oxide film (5 in FIG. 2D) and the surface of the semiconductor active layer 1c are aligned at the same level, the semiconductor active layer 1c is expected to rise. It is preferable to remove a part of.

  Next, after removing the photoresist (4 in FIG. 2C), the LOCOS oxide film 5 is formed in the element isolation region 8 by thermal oxidation using the silicon nitride film 3 as a mask, and then formed by thermal oxidation. The oxide film (not shown), the silicon nitride film (3 in FIG. 2C), and the silicon oxide film (2 in FIG. 2C) on the formed silicon nitride film 3 are removed (FIG. 2D). )reference). Thereby, a LOCOS oxide film 5 having a plurality of openings 5a is formed, and a gettering region 6 is formed in the semiconductor active layer 1c in the vicinity of the openings 5a.

  Next, a silicon oxide film 12 is formed on the semiconductor active layer 1c and the LOCOS oxide film 5, a silicon nitride film 13 is formed on the silicon oxide film 12, a photoresist 14 is coated on the silicon nitride film 13, and a photo The photoresist 14 is patterned into a predetermined shape by a lithography method (see FIG. 3E). Here, the photoresist 14 is formed on the semiconductor active layer 1c and the LOCOS oxide film 5 other than the region that will become the isolation trench (7 in FIG. 3F) in the future when viewed from the plane direction, and has a mesh shape. It is formed in a shape divided into (islands).

  Next, using the photoresist 14 as an etching mask, the silicon nitride film 13, the silicon oxide film 12, the LOCOS oxide film 5, and the semiconductor active layer 1c are removed by dry etching until the bonded insulating film 1b appears (FIG. 5). 3 (F)). Here, the isolation trench 7 is formed by removing the LOCOS oxide film 5 and the semiconductor active layer 1c.

  Next, after removing the photoresist 4, a silicon oxide film 7a is formed on the inner wall surface of the separation groove 7 by thermal oxidation (see FIG. 3G).

  Next, after filling polysilicon 7b in the isolation trench (7 in FIG. 3G; silicon oxide film 7a) by CVD, CMP is performed using the silicon nitride film (13 in FIG. 3G) as a stopper. Then, the silicon nitride film (13 in FIG. 3G) and the silicon oxide film (12 in FIG. 3G) are removed (see FIG. 3H). Thereafter, an element is formed in the element forming region 9 and further a wiring is formed (not shown). Although unnecessary polysilicon 7b is removed here by CMP, unnecessary polysilicon 7b may be removed by etch-back using dry etching.

  When the semiconductor device in the state of FIG. 2D is viewed from the planar direction, the LOCOS oxide film 5 formed in the element isolation region 8 has a large number of openings 5 a in a mesh shape (island shape) on the SOI substrate 1. . A number of depressions are formed in a mesh shape (net shape) on the SOI substrate 1 (on the semiconductor active layer 1c), and thermal oxidation is performed. Due to the stress accompanying thermal oxidation of the semiconductor active layer 1c (silicon), strain is generated in the Si crystal lattice in the semiconductor active layer 1c in the vicinity of the interface of the semiconductor active layer 1c / LOCOS oxide film 5. In particular, since there are a large number of openings 5a in the LOCOS oxide film 5 on the SOI substrate 1, the distortion of the crystal lattice is large in the vicinity of the center (when viewed from the plane) of each of the openings 5a. Thus, a large number of crystal defects are generated in the gettering region 6 in the semiconductor active layer 1c. This crystal defect can absorb heavy metal contaminants. The formation of the gettering region 6 does not require an ion implantation process, so that the manufacturing process does not increase.

(Embodiment 2)
As Embodiment 2 of the present invention, the shape of the opening 5a of the LOCOS oxide film 5 when viewed from the plane direction may be L-shaped, T-shaped, cross-shaped, arbitrary polygonal, or line-shaped.

1A is a partial cross-sectional view schematically showing a configuration of a semiconductor device according to Embodiment 1 of the present invention, and FIG. It is the 1st process partial sectional view showing typically the manufacturing method of the semiconductor device concerning Embodiment 1 of the present invention. It is the 2nd process fragmentary sectional view showing typically the manufacturing method of the semiconductor device concerning Embodiment 1 of the present invention. It is process partial sectional drawing which showed typically the manufacturing method of the semiconductor device which concerns on a prior art example.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 SOI substrate 1a Semiconductor wafer 1b Bonding insulating film 1c Semiconductor active layer 2, 12 Silicon oxide film 3, 13 Silicon nitride film 4, 14 Photoresist 5 LOCOS oxide film (insulating film)
5a Opening 6 Gettering region 7 Separation groove 7a Silicon oxide film 7b Polysilicon 8 Element isolation region 9 Element formation region 101 SOI substrate 101a Semiconductor wafer 101b Bonding insulating film 101c Semiconductor active layer 102 Oxide film 103 Nitride film 104 Photoresist 108 Gettering region 109 LOCOS oxide film 112 Isolation groove 113 Element isolation region

Claims (6)

An SOI substrate having a semiconductor active layer formed on a semiconductor wafer through an insulating film;
An insulating film disposed in an element isolation region around an element formation region of the SOI substrate, disposed on the semiconductor active layer, and having a plurality of mesh-shaped or line-shaped openings;
A gettering region disposed in the semiconductor active layer in the vicinity of the opening;
A semiconductor device comprising:   The semiconductor active layer is divided into islands for each element formation region, and an isolation groove is provided that penetrates the insulating film and the semiconductor active layer in the element isolation region and reaches the bonded insulating film. The semiconductor device according to claim 1.   3. The semiconductor device according to claim 1, wherein the insulating film having the opening is a LOCOS oxide film. A semiconductor active layer;
A LOCOS oxide film formed on an element isolation region on the semiconductor active layer and defining an element formation region, and having a plurality of openings;
A gettering region formed in the semiconductor active layer below the LOCOS oxide film corresponding to the opening;
A semiconductor device comprising: Forming a silicon oxide film and a silicon nitride film on an SOI substrate on which a semiconductor active layer is formed by bonding to a semiconductor wafer via an insulating film;
Forming a photoresist on the silicon nitride film over the entire surface of the element formation region of the SOI substrate and in the element isolation region in a mesh or a line;
Etching at least the silicon oxide film and the silicon nitride film until the semiconductor active layer appears using the photoresist as an etching mask;
After removing the photoresist, using the silicon nitride film as a mask, a LOCOS oxide film having a plurality of mesh or line openings for forming a gettering region in the element isolation region is formed by thermal oxidation. Forming, and
A method for manufacturing a semiconductor device, comprising:   Dividing the semiconductor active layer into islands for each element formation region, and forming an isolation trench that penetrates the LOCOS oxide film and the semiconductor active layer and reaches the bonded insulating film in the element isolation region; The method of manufacturing a semiconductor device according to claim 5, comprising:

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